On shutting down the computer a message appears on the screen saying ?Ending program rundll32.exe?. This is very annoying and slows down the shutdown process considerably. How can I stop this message from interrupting the shut down process? The computer is running Windows XP.

The ?rundll32.exe? process is responsible for running DLL (dynamic linked library) files, which contain shared code which different programs on the computer can use. DLL files are used to abstract particular code from programs. This means that if multiple programs need to access the same segment of code, they can just call one DLL file to obtain that code rather than having to duplicate the code in each individual program. The power of DLL files comes into play when programs attempt to access system functions (e.g. access the serial or USB ports on a computer) as Windows can provide DLL files that the programs can use for such functions, rather than the program designer needing to “reinvent the wheel” and write custom code for the functions.

Now that you understand the purpose of DLL files, we can investigate the reason that this error message is occurring on shutdown. Unfortunately the ?rundll32.exe? errors are quite difficult to diagnose, since the message does not say which DLL is causing the problem. Even if this information was presented, there is still no information on the program that is using the DLL, since the program using the DLL is most likely the process preventing that DLL from properly closing on shutdown. Therefore, we will need to try some procedures to narrow down the problem and determine the program or process causing the error.

First, viruses, spyware, and adware have been known to hide behind the ?rundll32.exe? process and cause the error being experienced on shutdown. Therefore, you should first complete a full virus scan and adware/spyware scan of the computer. If you don’t already have a virus scanner, I recommend you download and install AVG Anti-Virus Free (free.grisoft.com). For anti-adware and anti-spyware software, three good free utilities are Ad-Aware Free (www.lavasoft.de), Spybot Search & Destroy (www.safer-networking.org), and Windows Defender (www.microsoft.com/downloads). Once downloaded, run these utilities to detect any threats which may be installed on the computer.

Assuming the scans complete successfully and no threats are detected, you should next determine whether any programs or processes running in the Windows background are causing the problem. Restart the computer and, once the computer has restarted, immediately shutdown the computer. This will determine whether the problem is caused by a process which loads on startup, or a process or program which remains behind after the computer has been used for a session. For example, you use the computer for a session but one of the programs which you used does not close properly. If the problem occurs when you immediately shutdown the computer this indicates one of the processes loading on startup is likely causing the problem. To confirm, we will disable all the startup processes to see whether the problem continues. Restart the computer, and go to the “Start” menu > “Run” and type “msconfig” (without the quotes) and click OK. In the window that appears, click the “Startup” tab. This will list all the processes which load on Windows startup. Write down all the processes which are ticked (enabled), as you will need to re-enable these processes later, and then click “Disable All”. All startup processes are now disabled. Click OK and then restart the computer. Once the computer has restarted, immediately shutdown the computer. If the problem does not occur, we have confirmed the problem is being caused by one of the startup processes.

In this case, where the problem no longer occurs, you will need to determine the exact process causing the problem. This will be done through a process of elimination. Open the “msconfig” utility and then go to the “Startup” tab. Re-enable all the processes which were previously enabled. Click OK and then restart the computer. Now, press CTRL-ALT-DEL to open the Windows Task Manager. In the window that appears, click the “Processes” tab. Click the “User Name” heading to sort the processes by user name (if this column is not visible, go to the “View” menu > “Select Columns” and tick “User Name”). Close one of the processes running under your user name, and then restart the computer to see whether the error continues during the shutdown process. If so, repeat the procedure but close another process. Continue this procedure until the problem stops, at which time you know the process which is causing the problem. Once you have found the process you have several options. First, determine whether the program associated with the process is needed. If not, you could perhaps uninstall the program which should also uninstall the problem process. Alternatively, if you do need the program you could search Google with the process name for evidence of similar problems, and any potential resolutions.

However, in the event that the problem does not occur when you immediately shutdown the computer following a restart, this indicates that a startup process is not the cause of the problem. The next most likely cause is something which you have been using during the computer session that is not closing properly. To narrow down this problem, restart the computer (so that only the startup processes have loaded in the background). Open the Task Manager Processes tab, and write down all the processes running under your user name. Once this is done, proceed to use the computer as per a normal computer session. Once you have finished and are ready to shutdown the computer, open the Task Manager again and note down any new processes which are now running, that are not on your list of processes which were running when the computer initially started. Once this has been noted, shutdown the computer and presumably the error will appear. It is highly likely the error is being caused by one of those new processes.

To determine exactly which one of those processes is causing the problem, you will first need to determine what each process does. If this is not evident from the name, use Google to search for the process name to determine the program which is related to the process. Once you have compiled a list of the programs, restart the computer and then start one of those programs, use the program for a few minutes, and then close the program. Using the Task Manager, check whether the process is still running in the background. If so, restart the computer and check whether the problem occurs during the shutdown process. If the problem does not occur, repeat this process with another one of the programs. Be aware, if the process does not continue running after the program has been closed this may indicate that you have not done something that you usually do within the program (which causes the process to remain open). So, try to mimic your usage of the programs as accurately as possible to provide an accurate testing scenario.

Having determined the program causing the problem, your best resolution will be to search Google to determine whether other people are experiencing a similar problem and whether any resolutions are available. Should this not produce a result, please contact me with the details of the program and process causing the problem, and I will check whether there is any additional information which may be useful to resolve the problem.